if you are looking for a clear 1-1 relationship between gear and materia you will not find it anywhere on the internet. There is no guarantee that a particular piece of equipment will yield a specific materia, although the equipment themselves have a natural tendency to generate a fixed set of materia types.
There are many databases available right now if you simply do a google search for materia ffxiv. Keep in mind these are all individual's efforts at trying to collect a large enough database to give ppl a grasp of the degree of variability in materia generation.
Just as a side note.. these databases are also very useful for people simply interested in making a lot of gil in a short amount of time. The only work required is to keep up to date with the current "trend" and play the markets =P i.e. the price of dated velveteen longsash jumped from 20-30k to 100k+ in less than 2 weeks when it was confirmed they converted to heaven's fist materia. Other pieces of gear that yield relatively rare materia like healer's hand and savage might materia go through similar phases. Materia is the new frenzy! you can jump in now or make a killing off others caught up in the hype =P